1. Field of the Invention
The present invention relates generally to soda-lime glass batch formulations including ash from the combustion of coal as a constituent, and further to methods of producing soda-lime glass by adding the coal ash to the batch constituents prior to melting or to the molten glass in the furnace.
2. Description of the Prior Art
Soda-lime glass is a term applied generally to one of the more common, utilitarian groups of glass formulations. Glass containers, table ware, lighting materials and flat glass are commonly produced from varying formulations of soda-lime glass. Typical ranges of constituents in representative formulations are:
Lime Tableware Glass and Flat Glass Containers Lamp Bulbs Sheet & Plate % by wt. % by wt. % by wt. ______________________________________ SiO.sub.2 71.5 - 73.5 70.0 - 72.5 71.0 - 73.0 Al.sub.2 O.sub.3 .4 - 2.2 .3 - 2.6 .5 - 1.5 CaO 7.8 - 10.8 5.4 - 6.5 8.0 - 11.0 MgO .0 - 3.6 3.0 - 4.5 1.0 - 4.0 BaO .0 - .5 -- -- Na.sub.2 O 12.5 - 15.5 15.8 - 17.0 13.0 - 15.0 K.sub.2 O .4 - 1.0 .3 - 1.2 .3 - .8 B.sub.2 O.sub.3 .0 - .2 .0 - .5 -- Fe.sub.2 O.sub.3 .04 - .05 .03 - .04 .06 - .1 ______________________________________
The above basic formulations are for essentially uncolored glasses. Color is typically provided by adding additional iron sulfur trioxide or carbon, for instance.
Various other ingredients are often added to aid in the melting, refining, processing or coloring of the resulting glass. For instance, as an example of an unlikely constituent, slag from steel manufacture has been added in varying amounts. However, no prior use of coal ash as a constituent in soda-lime glass has been found.
Ash is the nonvolatile, noncombustible matter in coal. Ash thus remains after coal is burned. It typically constitutes on the order of 10 percent by weight of, for instance, western sub-bituminous coal.
Fine or fly ash is formed by burning coal in a pulverous form entrained in air. The resulting ash is in the form of small particles. Historically fly ash has been dissipated through stacks. However, with the increased use of scrubbers to remove the fly ash from the stack gases, substantially greater amounts of fly ash are being collected.